[asterisk-users] ISDN30 and digital phones

Tim Panton tim at mexuar.com
Wed Sep 27 05:04:47 MST 2006

On 27 Sep 2006, at 10:56, Mike Williams wrote:

> Hi,
> At our other site in the UK we currently have a rather old Nortel  
> BCM (4000 I
> think), with an ISDN30 feed and 15-16 or so digital extensions  
> (Meridian of
> some description).
> The ISDN comes in as HSDSL over a twisted copper pair to a small BT  
> box, then
> ethernet to the BCM.
> We'd like to do, at least, inter-office VoIP calls. However I  
> believe making
> trunks between asterisk and BCM isn't the easiest thing in the  
> world, and my
> brief exploration of the BCM configuration bears that out. Plus we  
> don't have
> any licences for VoIP.
> If I were to recommend replacing the BCM with an asterisk machine,  
> what
> special hardware/cards would I need? (I so don't understand how US  
> line
> designations fit in with UK style lines)
> I'm open to replacing phones if the kit to interface with digital  
> phones costs
> more than buying SIP phones, every desk already has at least 2  
> cat5e points.

One way you could do this would be to put an asterisk box in between the
Meridian and the ISDN30. You put a dual (or quad) E1 card into the
asterisk machine.

You then write a simple dialplan that (by default) passes all calls  
through the asterisk machine untouched.

Once you have that working, you add rules such that outgoing calls
to your other offices are excluded from this process and sent via VOIP.

Done right the Nortel will be blissfully unaware of the fact that the
asterisk box is even there. (over time you can add features/ 
to the VOIP area - voicemail , call monitoring  etc.)

No new phones, no new hardware except the asterisk system.
You _should_ even be able to do faxing on the Nortel, provided
you prevent the asterisk machine from doing echo canceling
on fax calls.

The only down-side is that you only get 30 channels to your asterisk,  
given that you have only 16 extensions anyway....


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